The present invention relates to a method and apparatus for guying a load bearing member, and more particularly, to a method and apparatus for preventing overstressing of one or more of a plurality of guys opposing a force exerted on the load bearing member.
Towers are employed in a variety of applications in industry to support loads above the ground. Typically a force is imposed on a tower in a direction transverse to its upright dimension by a catenary cable strung between the tower and a remote location. In addition to the weight of the cable, loads are normally suspended from the catenary cable, thereby increasing the force imposed on the tower. Guys, strung between the tower and suitable anchors, are conventionally employed to counteract at least a portion of these forces imposed on the tower.
In a simple tower guying system, guys are arrayed in the plan view so that a first one of the guys extends rearwardly from the tower in a direction substantially opposite to the direction in which the force from the catenary cable is exerted on the tower. The remaining guys are deployed sidewardly from the tower and at an angle in the plan view from the first guy. In elevation view all of the guys are of the same length and are oriented at equal angles relative to direction of the forces on the tower. As an increasing force is exerted on the tower by the catenary cable, each of the guys bears a load approximately proportional to the cosine of the angle it makes in the plan view with the direction in which the force is exerted on the tower. Thus, the first guy extending rearwardly in a direction opposite to the direction of the force on the tower will carry the greatest tension load opposing the force on the tower.
As the force on the tower is increase, the tension loads in the guys will increase. Since the sidewardly extending guys bear a lesser proportion of the total opposing load, the stress in the rearwardly extending guy can reach its ultimate strength before the remaining guys, causing the rearwardly extending guy to fail and requiring the sidewardly extending guys to bear the entire tension load created by the primary load exerted on the tower. Assuming that the sidewardly extending guys are the same size as the rearwardly extending guy, this condition will overstress the sidewardly extending guys and will also cause them to fail, in turn allowing the tower to topple with potentially harmful results.
Accordingly, in a system for guying a load bearing member it is an object of the present invention to provide a method and apparatus for limiting the stress exerted on a guy opposing a variable force exerted on the load bearing member; to provide a method and apparatus for transferring a portion of the tension load otherwise being borne by the guy bearing the greatest tension load to one or more adjacent guys that normally bear a leser tension load; and to provide a method and apparatus for maintaining the tension load in the guy normally bearing the greatest tension load at a predetermined maximum value while increasing the tension load in one or more adjacent guys.